Electrical primers



Feb. 6, 1962 A. KASPAUL 3,019,732

ELECTRICAL PRIMERS Filed Oct. 21, 1958 Patented Feb 6, 1&652

The present invention relates to electrical primers and it is moreespecially, but not exclusively, concerned with primers for setting oiia propelling charge or bursting charge.

The chief object of this invention is to provide a primer device of thisle'nd which is better adapted to meet the requirements of practice thanthose used up to the present time and, in particular, which is easier tobe checked up and less sensitive to stray currents.

A primer device according to this invention includes a sensitive chargeand two electrodes adapted to be connected with the two terminalsrespectively of a source of electric voltage and it is characterized bythe fact of interposing, between these electrodes and in contact withsaid charge, a body or" a semi-conductor material, said body being sochosen and dimensioned that the flow of current therethrough producestherein a spark capable of igniting said charge.

The term semi-conductor material is used in the present application todesignate a solid body having a crystallized structure, which is aninsulator at temperatures close to the absolute zero but which, athigher temperatures, either has an electronic conductivity that can beeasily detected or acquires such a conductivity under the effect of adisturbance of its ideal crystallized structure, or again can be madeconductive, for instance when it is subjected to an external influence.

These semi-conductor materials are characterized in that at least withinsome ranges of temperature their resistance decreases when thetemperature rises, in opposition to what takes place in the case ofmetallic conductors.

Preferred embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawing, given merely byway of example and in which:

FIGS. 1 and 2 of this drawing show, in axial section, two electricprimer devices made according to diiierent embodiments of the presentinvention.

The primer device shown by the drawing includes a source of electricvoltage in the form of a condenser 1 adapted to be charged in advance.

The primer device, according to the invention, essentially includes twometal electrodes 2 and 3 adapted to be connected respectively to the twoterminals of condenser 1 and, interposed between these electrodes, anelement t of a semi-conductor material chosen and dimensioned in suchmanner that the flow of electric current from said condenser l andthrough said electrodes 2 and 3 produces in element 4 a spark capable ofsetting off a sensitive charge 5 placed in contact with said element 4.

Advantageously, according to this invention, the semiconductor is eithera metalloid or an anhydride of a metalloid having a relatively lowmelting point and preferably a boiling point such that it can beevaporated under vacuum. For instance, this element consists of selenium(Se), germanium (Ge), vanadium pentoxide (V or silicon monoxide (SiO).

Other bodies may be used, for instance:

Silicon (Si) Silicon bioxide-or silica-($0 Silicon sesquioxide (SiO-SiO2 Calcium silicate (CaO-SiO Cerium bioxide (CeO Cadmium sulphide (CdS)Cadmium selenide (CdSe) Antimony sesquisulphide (Sb S' Aluminum antimony(Al-Sb) Gallium antimony (Ga-Sb) Uranium bioxide (U0 Cadmium oxisulphide(CdS-CdO) Cadmium oxiselenide (CdSe-CdO) Advantageously, thesemi-conductor material is in the form of a thin film or layer 4 atleast a small area of which (for instance averaging a fraction of asquare millimeter) has one of its faces in contact with one electrode,the other of saidfaces being in contact with the other electrode. Thethickness of the layer of semiconductor material thus inserted betweenthe electrodes will be determined experimentally in every case so as toobtain the desired result. In the particular case where the voltagesupplied by the source is close to volts (capacity averaging 2 at),satisfactory results have been obtained with a thickness averaging 1micron.

The film 4- of semi-conductor material is advantageously deposited bythe known method of evaporation under a high vacuum which makes itpossible to obtain a layer of accurate and regular thickness owing tothe measurement of the amount of material to be evaporated and to thecontrol of the time of action of the jets of vapour during theevaporation of the semi-conductor material.

According to one advantageous embodiment of the invention, one of theelectrodes (2) is in the form of an axial rod the upper end of which hasa very small area (for instance less than 0.2 mm. This electrode issupported by an insulating filler 6 (for instance of a ceramic materialor a synthetic resin) suitably chosen so that layer 4 can be depositedin good condition upon its fiat upper surface which is at the same levelas the top end of electrode 2. This insulating material is packed in acylindrical sleeve 3 made of a conductor material which constitutes thesecond electrode. This sleeve 3 is disposed coaxially with electrode 2.In the particular case above referred to, the inner diameter of sleeve 3was 8 mm.

Of course, means must be provided for feeding current from sleeve 3 tothe portion of the upper surface of film 4 located opposite the portionof the under surface of said film 4 that is in contact with the top endof electrode 2. Such means must be such that the heat of the sparkproduced in film 4 between these two surface portions s transmitteddirectly to the primary charge 5 which Is supposed to b disposed abovefilm t.

in the construction of FIG. 1, the whole upper surface of film 4 iscovered by a thin conductor layer 7 in electric contact at least over aportion of its edges with the inner surface of sleeve 3, this layer 7being advantagesously deposited by evaporation under a high vacuum, asabove described with reference to film 4.

Advantageously, layer 7 is made of a suitable metal capable of beingevaporated in a vacuum, preferably at a temperature higher than that ofthe semiconductor material that has been previously disposed on theinsulator 6. Indium is a particularly advantageous metal to constitutelayer 7, due to its relatively low melting point (156 C.) and to itshigh boiling point (above 1,400 C.). Furthermore, it can easily beeva-orated under a vacuum. This metal has, with respect to atmosphericagents, qualities of stability comparable to that of silver, the meltingpoint of which is six times higher. Furthermore, indium is a ductilemetal. it deposits, by evaporation, in a granular form but very adhesiveto film 4.

Anyway, it is advantageous to provide, above layer 7, a ring 8 made of aconductive material which is forced into sleeve 3. This ring, which istightly applied against layer 7, ensures a good electric contact betweensleeve 3 and layer 7. The inside of said ring may constitute a housingfor the primary charge which is suitably compressed.

it will be readily understood that with such an arrangement, a smallcentral portion of film 4 is inserted between the two electrodes and thespark will thus be produced in this portion of filn1'4, which spark willpass through layer "7, if the thickness thereof is suitably chosen, andwill set oil charge 5.

For practical purposes, the thickness of layer 7 may be very small. Itwill be chosen sufficient to permit the passage therethrough of the"current which is to produce the ignition spark in the semi-conductormaterial. A layer of indium having a thickness ranging from V2 micron to1 micron gave good results. i

According to the embodiment of FIG. 2, sleeve 3 carries a finger 9 of aconductor material extending radially and the end of which is in contactwith the portion of film 4 located above the upper end of electrode 2.Charge 5 is then compressed directly above film 4 and finger 9.

It Will be understood that in this case the spark that is n electrodesto complete a circuit between the two electrodes to allow an electriccharge of said predetermined potential to penetrate therethrough andignite said sensitive primary charge and to dissipate an electric chargeof less than said predetermined potential.

2. An electric primer device adapted to be fired by a flow of electricalcurrent from a source of electrical voltage comprising in combination asensitive primary charge, two electrodes, one of said two electrodescomprising the outer metal surface of the primer device and parallel tothe second of said two electrodes, said second electrode being locatedaxially of said first electrode, a plastic insulating material disposedaround said second electrode,

both electrodes adapted to be connected to a voltage source, asemi-conductive material, said material being selected from the groupconsisting of Se, Ge, V 0 SiO,

electric charge of sufiicient potential can penetrate the rsemi-conductive material and base material and ignite produced in film'4, between the end of finger 9 and the axial electrode 2, can directlyset off the primary charge 5.

The primer device above described is very simple to manufacture and itgives very constant results due, in particular, to the possibilitiesgiven by the semi-conductor materials of accurately adjusting thesensitiveness thereof.

Furthermore, such primer devices have an electrical resistance that canbe easily measured, which is interesting for checking up purposes. Sucha checking up can be effected by passing through the device a currentunder a voltage lower than the limit voltage which would produce theelectric spark.

By way of example, it will be indicated that this limit voltage is onlyvolts in the case of an indium layer 1 micron thick and of a layer ofSiO-Si0 0.5 micron thick.

As a matter of fact, the initial electrical resistance of the primerdevice, before the explosive charge is in place, is generally high. Butafter said charge has been placed and compressed on film 4, theelectrical resistance is greatly reduced and becomes easy to measure.

Finally, such primer devices are very little sensitive to stray currentsdue to static or friction electricity, which currents can be dischargedby passing, without producing a spark, through the semi-conductormaterial.

The manufacture of such primer devices is easy, their mechanicalrigidity is satisfactory and there is no difficulty in complying withthe tolerances during their manufacture. e

In a general manner, while'I have, in the above description, disclosedwhat I deem to be practical and elficient embodiments of my invention,it should be well understood that I do not wish to be limited thereto asthere might be changes made in the'arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is:

1. An electric primer adapted to be fired by a flow of electricalcurrent from a source of electrical voltage which comprises incombination, a sensitive primary charge adapted to be exploded by anelectrical discharge of predetermined high potential, two electrodesdisposed adjacent to said sensitive charge, both electrodes adapted tobe connected with a source of electrical energy, a semiconductivematerial, said material being selected from the group consisting of Se,Ge, V 0 SiO, Si, SiO SiO-SiO CaO-SiO CeO CdS, CdSe, Sb S Al-Sb, Ga-Sb,U0 CdS-CdO, CdSe-CdO, said semi-conductive material abutting saidsensitive charge and electrically coupled with said said sensitivecharged primary.

3. An electrical primer device adapted to be fired by a flow of electriccurrent from a source of electrical voltage comprising in combination asensitive primary charge, two electrodes, said electrodes adapted to beconnected to a voltage source, the first said electrode forming theouter casing of the primer device, a semi-conductor layer, said materialbeing selected from the group consisting of Se, Ge, V 0 SiO, Si, SiOSiO-SiO CaO-SiO Ce0 CdS, CdSe,' Sb S Al-Sb, Ga-Sb, U0 CdS-CdO, CdSe-CdO,a conductive material supporting said semi-conductor layer, thecombination of said semi-conductor and conductive material beingattached to the periphery of said first electrode casing and locatedsuch that an electric charge of sufficient potential from the second ofsaid two electrodes can penetrate the semi-conductive material and basematerial and ignite said sensitive charged primary.

4. An electrical primer device adapted to be fired by the flow ofelectric current from a source of electrical voltage comprising incombination a sensitive primary charge, two electrodes, said electrodesadapted to be attached to an electric voltage of predeterminedpotential, one of said electrodes forming the outer casing of the primerdevice, a semi-conductor material, said material being selected from thegroup consisting of Se, Ge, V 0 SiO, Si, SiO SiO-SiO CaO-SiO 0e0 CdS,CdSe, 812 8 Al-Sb, Ga-Sb, U0 CdS-CdO, CdSe-CdO, said material beingattached to said first electrode and located such that an electriccharge of sufiicient potential from the second of said two electrodescan penetrate the semiconductive material to ignite said sensitivecharged primary, an annular conductance ring, said ring encasing saidprimary charge and maintaining positive electrical contact between saidfirst electrode and said semi-conductive material.

References Cited in the file of this patent UNITED STATES PATENTS319,627 Russell June 9, 1885 319,628 Russell June 9, 1885 2,021,661Kisfaludy Nov. 19, 1935 2,676,117 Colbert Apr. 20, 1954 2,696,191Sheehan Dec. 7, 1954 2,708,877 Smits May 24, 1955 2,754,757 MacLeod July17, 1956 2,762,302 MacLeod Sept. 11, 1956 FOREIGN PATENTS 982,837 FranceJan. 31, 1951

1. AN ELECTRIC PRIMER ADAPTED TO BE FIRED BY A FLOW OF ELECTRICALCURRENT FROM A SOURCE OF ELECTRICAL VOLTAGE WHICH COMPRISES INCOMBINATION, A SENSITIVE PRIMARY CHARGE ADAPTED TO BE EXPLODED BY ANELECTRICAL DISCHARGE OF PREDETERMINED HIGH POTENTIAL, TWO ELECTRODESDISPOSED ADJACENT TO SAID SENSITIVE CHARGE, BOTH ELECTRODES ADAPTED TOBE CONNECTED WITH A SOURCE OF ELECTRIAL ENERGY, A SEMICONDUCTIVEMATERIAL, SAID MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF SE,GE, V2O5, SIO, SI, SIO2, SIO-SIO2, CAO-SIO2, CEO2, CDS, CDSE, SB2S3,AL-SB, GA-SB, UO2, CDS-CDO, CDSE-CDO, SAID SEMI-CONDUCTIVE MATERIALABUTTING SAID SENSITIVE CHARGE AND ELECTRICALLY COUPLED WITH SAIDELECTRODES TO COMPLETE A CIRCUIT BETWEEN THE TWO ELECTRODES TO ALLOW ANELECTRIC CHARGE OF SAID PREDETERMINED POTENTIAL TO PENETRATETHERETHROUGH AND IGNITE SAID SENSITIVE PRIMARY CHARGE AND TO DISSIPATEAN ELECTRIC CHARGE OF LESS THAN SAID PREDETERMINED POTENTIAL.